Manufacture of incandescent lamps.



UNITED STATES, PATENT OFFICE.

FRITZ BIIAU, OF CHARLOTTEMURG, GERMANY, ASSIGNOR TO GENERAL ELEGTBIO COMPANY, A CORPORATION OF NEW YORK.

MANUFACTURE OF INCANDESCENT LAMPS.

Specification of Letters Iatent. Patented June 11 1918, Application filed April 18,1916. Serial No. 91,961.

No Drawing.

To all whom it may concern:

Be it known that I, Fm'rz BLAU, a citizen of the Empire of Austria-Hungary, residing at Charlottenburg, Germany, have in- 6 vented certain new and useful Improvements" in the Manufacturev of Incandescent Lamps, of which the following is a specification.

My invention relates to incandescent lamps, particularly lamps with metal filarments, and its ob ect is to provide in the lamp 9. very efiicient drying agentwhich will remove or render-harmless the water vapor in the lamp,*and thereby produce an improved lamp.

t has been proposed that special means be employed in order to remove from incandescent lamps during the process of manulecture not only the residual gas but also the residual moisture. To this end the lamps are usually heated while being evacuated, and it has also been proposed to introduce some kind of drying agent into the lamp. Many of the drymg agents now known are, however, subject to the disadvantage that they absorb moisture before they are intro- -duced into the lamps, and consequently'have lost a great deal of their efliciency by the time they are put 'into the lamp. nder some conditions, the drying agent absorbs so much moisture during the process of manufacture and prior to the exhaustion of the lamp that the drying agent cannot fulfil its purpose, and in some cases even gives up in the lamp some of the moisture which mg the opposite efiect from that which is intended. One dryin pentoxid, which has een proposed hasin addition the further disadvantage that it is volatile and consequently requires elaborate it has previously absorbed, thereby produc-' agent, phosphorous the manufacture of the lamp or heat especially applied'for the purpose, undergo a profound chemical change or decomposition which produces'in the lamp a very eflicient drying agent. For example, it is known that the anhydrous oxids of the alkali metals and of the alkaline earth metals, especially of barium, are very eflicie'nt drylng agents. This is also themselves. 'If one should attempt to use these substances in the usual manner the above mentioned disadvantageswould be encountered, but this is not true if they are used in accordance with my invention. If, for example, barium oxid'is to be used as a g agent in accordance with my invention, a barium compound decomposable by heat is introduced into the incandescent lamp. 'azoimid, BaN,. This salt may be introduced into the lamp either in a dry condition or in an aqueous solution. In the latter case, the water is removed by evaporation after the salt is'in place. If the incandescent lamp is now evacuated, and heated to the proper temperature, the barium a zoimid decomposes with the evolution of nitrogen and leaves in the. lamp a deposit of metallic true of the corresponding metals Among such" compounds is barium barium. If the heating is then further continned and an oxidizing medium or oxygen containing gas, such as dry air, is admitted to the lamp, the metaIIic barium' is transprovided with the desired drying agent manufactured directly in the lamp.

The procedure may be such that the decomposition of .the metallic compound, such as barium azoimid, goes on from the beginning in the presence of air, which case barium oxid is formed without any perceptible intermediate formation of metallic barium.

If, in the exam 1e first described, the introduction of oxi izing gas is omitted, an incandescent lam tains metallic barlum as an efiective drying agent.

Other salts of hydrazoic acid act like barium azoimid, as for example, the corresponding compounds of the alkalis and of the alkaline earths, but barium azoimid gives very good results, and thereforevthe use of it has been described asan example of one embodiment of my lnvention.

What I claim as new and deslre to secure by Letters Patent of the United States, is,-

composed, and heating the envelop of the lamp to decompose said compound.

2. The method which consists in introducing into an incandescent lamp a salt of barium and hydrazoic acid, and heating the lamp to decompose saidsalt.

3. The method which consists in introducing into an incandescent lamp barium a'zoimid BaN and heating the lamp to decompose said barium azoimid.

, 4. The method which consists in introducing into a lamp a salt of an alkali or alkaline earth metal and hydrazoic acid, which is decomposable to leave a residue of. said metal at a temperature between room temperature and'the temperature at which glass softens, heating the lamp to decompose said salt, and oxidizing the metallic residue to form a drying agent.

5. The method which consists in introducing into an incandescent lampa metallic salt decomposable at a temperature between room temperature and the temperature at which glass softensand leaving a metallic residue in the lampwhen decomposed, and heating the glass of the lamp to produce decomposition of said salt.

6. An incandescent lamp comprising a sealed envelop, a filament therein, and metallic barium on the interior surface of said envelop.

7. An incandescent lamp'having a sealed envelop, a filament therein, and anhydrous oxid of barium in said envelop.

In witness whereof, I have hereunto set my hand this thirteenth day of March, 1916.

FRITZ BLAU. 

